Network Working Group A. Melnikov Internet-Draft Isode Ltd Intended status: Informational B. Hoeneisen Expires: 17 August 2023 pEp Foundation 13 February 2023 IANA Registration of Content-Disposition Header Field value 'encapsulated' draft-melnikov-iana-reg-cd-encapsulated-00 Abstract This document defines a new Content-Disposition header field value "encapsulated" to be used with "message/rfc822" and "message/global" media types. Content-Disposition "encapsulated" signals that enclosed message should be presented inline, instead of being presented as a forwarded message. One use case for this is for S/ MIME header protection. About This Document This note is to be removed before publishing as an RFC. Status information for this document may be found at https://datatracker.ietf.org/doc/draft-melnikov-iana-reg-cd- encapsulated/. Discussion of this document takes place on the dispatch non-WG mailing list (mailto:dispatch@ietf.org), which is archived at https://mailarchive.ietf.org/arch/browse/dispatch/. Source for this draft and an issue tracker can be found at https://gitea.pep.foundation/pEp.foundation/internet-drafts. Status of This Memo This Internet-Draft is submitted in full conformance with the provisions of BCP 78 and BCP 79. Internet-Drafts are working documents of the Internet Engineering Task Force (IETF). Note that other groups may also distribute working documents as Internet-Drafts. The list of current Internet- Drafts is at https://datatracker.ietf.org/drafts/current/. Melnikov & Hoeneisen Expires 17 August 2023 [Page 1] Internet-Draft Content-Disposition 'encapsulated' February 2023 Internet-Drafts are draft documents valid for a maximum of six months and may be updated, replaced, or obsoleted by other documents at any time. It is inappropriate to use Internet-Drafts as reference material or to cite them other than as "work in progress." This Internet-Draft will expire on 17 August 2023. Copyright Notice Copyright (c) 2023 IETF Trust and the persons identified as the document authors. All rights reserved. This document is subject to BCP 78 and the IETF Trust's Legal Provisions Relating to IETF Documents (https://trustee.ietf.org/ license-info) in effect on the date of publication of this document. Please review these documents carefully, as they describe your rights and restrictions with respect to this document. Code Components extracted from this document must include Revised BSD License text as described in Section 4.e of the Trust Legal Provisions and are provided without warranty as described in the Revised BSD License. Table of Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3 1.1. Use Cases . . . . . . . . . . . . . . . . . . . . . . . . 3 1.2. Implementations . . . . . . . . . . . . . . . . . . . . . 3 1.3. Requirements Language . . . . . . . . . . . . . . . . . . 3 1.4. Terms . . . . . . . . . . . . . . . . . . . . . . . . . . 4 2. Specification . . . . . . . . . . . . . . . . . . . . . . . . 4 3. Example . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 4. Security Considerations . . . . . . . . . . . . . . . . . . . 5 5. Privacy Considerations . . . . . . . . . . . . . . . . . . . 5 6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 5 7. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 6 8. References . . . . . . . . . . . . . . . . . . . . . . . . . 6 8.1. Normative References . . . . . . . . . . . . . . . . . . 6 8.2. Informative References . . . . . . . . . . . . . . . . . 6 Appendix A. Document Changelog . . . . . . . . . . . . . . . . . 7 Appendix B. Open Issues . . . . . . . . . . . . . . . . . . . . 7 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 7 Melnikov & Hoeneisen Expires 17 August 2023 [Page 2] Internet-Draft Content-Disposition 'encapsulated' February 2023 1. Introduction This document defines a new Content-Disposition header field [RFC2183] value "encapsulated" to be used with "message/rfc822" [RFC2046] and "message/global" [RFC6532] media types. The value "encapsulated" is meaningful when used within S/MIME or PGP/MIME signed or encrypted body parts (e.g., as specified in [I-D.ietf-lamps-header-protection] for S/MIME). Absence of Content- Disposition header field (or presence of any value other than "encapsulated") when Content-Type is "message/rfc822" or "message/ global" means that the message nested inside "message/rfc822" (or "message/global") is a simple forwarded message. Presence of "Content-Disposition: encapsulated" means that encapsulation is used for header protection, but otherwise the message should be displayed inline. 1.1. Use Cases Two use cases have been discovered so far: 1. This Content-Disposition value indicates whether a nested message is signed and/or encrypted (S/MIME or PGP/MIME), which tells the receiving side how to display the message to the user. Currently, many email clients display "weird artefacts" to users due to this missing information. 2. This Content-Disposition values indicates to mailing lists which signed and/or encrypted (S/MIME or PGP/MIME) email messages are forwarded, and which are just encapsulated for the purpose of header protection, and how to handle these respective messages. 1.2. Implementations At this time, the following email systems are known to use this Content-Disposition header field value: 1. Isode Harrier Web Server with S/MIME [RFC8551] support 1.3. Requirements Language The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in BCP 14 [RFC2119] [RFC8174] when, and only when, they appear in all capitals, as shown here. Melnikov & Hoeneisen Expires 17 August 2023 [Page 3] Internet-Draft Content-Disposition 'encapsulated' February 2023 1.4. Terms The following terms are defined for the scope of this document: * Header Field (HF): cf. [RFC5322] * Header Section (HS): cf. [RFC5322] 2. Specification This section defines the new "encapsulated" Content-Disposition header field value. An implementation that supports Content-Disposition header field as defined in [RFC2183], but doesn't support this specification will interpret "encapsulated" in the same way as the value "attachment" (as per requirements in [RFC2183]). An implementation that supports this specification uses the Content- Disposition value "encapsulated" with Content-Type "message/rfc822" or "message/global" to signal that the message is encapsulated for header protection (cf. [I-D.ietf-lamps-header-protection]). Presence of Content-Disposition "encapsulated" with any other Content-Type should be treated in the same way as the Content- Disposition value "inline". 3. Example The following example shows the usage of the Content-Disposition header field value "encapsulated" for an email message that is not forwarded, but encapsulated in another email message. Melnikov & Hoeneisen Expires 17 August 2023 [Page 4] Internet-Draft Content-Disposition 'encapsulated' February 2023 Date: Mon, 25 Sep 2017 17:31:42 +0100 (GMT Daylight Time) Message-ID: Subject: Meeting at my place From: "Alexey Melnikov" MIME-Version: 1.0 Content-Type: multipart/signed; charset=us-ascii; micalg=sha1; protocol="application/pkcs7-signature"; boundary=.cbe16d2a-e1a3-4220-b821-38348fc97237 This is a multipart message in MIME format. --.cbe16d2a-e1a3-4220-b821-38348fc97237 Content-Type: message/rfc822 Content-Disposition: encapsulated Date: Mon, 25 Sep 2017 17:31:42 +0100 (GMT Daylight Time) From: "Alexey Melnikov" Message-ID: MIME-Version: 1.0 MMHS-Primary-Precedence: 3 Subject: Meeting at my place To: somebody@example.net X-Mailer: Example Mailer Content-Type: text/plain; charset=us-ascii This is an important message that I don't want to be modified. --.cbe16d2a-e1a3-4220-b821-38348fc97237 Content-Transfer-Encoding: base64 Content-Type: application/pkcs7-signature [[base-64 encoded signature]] --.cbe16d2a-e1a3-4220-b821-38348fc97237-- 4. Security Considerations This document does not define a new protocol, and thus does not create new security concerns in and of itself. 5. Privacy Considerations This document does not introduce any new issues regarding Privacy. 6. IANA Considerations This document requests IANA to register the Content-Disposition header field value [RFC2183] "encapsulated" with the reference [RFC THIS]. Melnikov & Hoeneisen Expires 17 August 2023 [Page 5] Internet-Draft Content-Disposition 'encapsulated' February 2023 [[ RFC Editor: Replace [RFC THIS] with the number of this RFC before publication. ]] 7. Acknowledgments The authors would like to thank the following people who have provided helpful comments and suggestions for this document: David Wilson, Kelly Bristol, Krista Bennett, Robert Williams, Steve Kille, and Wei Chuang. 8. References 8.1. Normative References [RFC2046] Freed, N. and N. Borenstein, "Multipurpose Internet Mail Extensions (MIME) Part Two: Media Types", RFC 2046, DOI 10.17487/RFC2046, November 1996, . [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, DOI 10.17487/RFC2119, March 1997, . [RFC2183] Troost, R., Dorner, S., and K. Moore, Ed., "Communicating Presentation Information in Internet Messages: The Content-Disposition Header Field", RFC 2183, DOI 10.17487/RFC2183, August 1997, . [RFC5322] Resnick, P., Ed., "Internet Message Format", RFC 5322, DOI 10.17487/RFC5322, October 2008, . [RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC 2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174, May 2017, . [RFC8551] Schaad, J., Ramsdell, B., and S. Turner, "Secure/ Multipurpose Internet Mail Extensions (S/MIME) Version 4.0 Message Specification", RFC 8551, DOI 10.17487/RFC8551, April 2019, . 8.2. Informative References [I-D.ietf-lamps-header-protection] Gillmor, D. K., Hoeneisen, B., and A. Melnikov, "Header Protection for S/MIME", Work in Progress, Internet-Draft, Melnikov & Hoeneisen Expires 17 August 2023 [Page 6] Internet-Draft Content-Disposition 'encapsulated' February 2023 draft-ietf-lamps-header-protection-11, 24 January 2023, . [RFC6532] Yang, A., Steele, S., and N. Freed, "Internationalized Email Headers", RFC 6532, DOI 10.17487/RFC6532, February 2012, . Appendix A. Document Changelog [[ RFC Editor: This section is to be removed before publication ]] * draft-melnikov-iana-reg-cd-encapsulated-00 - Renamed document - Replaced Content-Type forwarded parameter with Content- Disposition "encapsulated" * draft-melnikov-iana-reg-forwarded-00 - Initial version derived from draft-ietf-lamps-header- protection-requirements-01 Appendix B. Open Issues [[ RFC Editor: This section should be empty and is to be removed before publication. ]] Authors' Addresses Alexey Melnikov Isode Ltd 14 Castle Mews Hampton, Middlesex TW12 2NP United Kingdom Email: alexey.melnikov@isode.com Bernie Hoeneisen pEp Foundation Oberer Graben 4 CH- 8400 Winterthur Switzerland Email: bernie.hoeneisen@pep.foundation URI: https://pep.foundation/ Melnikov & Hoeneisen Expires 17 August 2023 [Page 7]